As you can see above, I can’t type the letter 'I' alone without it turning into A. Perhaps this is a bug in Apple’s iOS 11.1. It doesn’t permit the user to key the alphabet 'I'. When you type ‘I’, it immediately shows as ‘A’. One of the major reasons for this problem is the functionality of autocorrect software or sometimes even because of the emojis. Many users often get an 'I' when they turn out to be frequent users of emoji. However, you can fix this problem although not permanently yet for a short time or temporarily.
Go to ‘Settings’ in the ‘General’ tab and choose the keyboard option from the settings.
Under the keyboard, you have a lot of options like: Auto-Capitalization, Auto-correction. Navigate to the text replacement and choose that option which is right below the keyboard option.
Tap the plus sign. You can see two text boxes. The upper text box shows the phrase. Inside the ‘Phrase’, type an uppercase 'I'.
Below the phrase box, there is another box denoted by ‘Shortcut’. Click the shortcut and type lowercase ‘I’.
By doing this, you can override autocorrect. So, whenever you type a lower case ‘I’, it will automatically change to the upper case. For most cases, your problem will be solved. This issue will soon be sorted out by Apple and you can expect this in the upcoming software update.